Peroxisomes

Peroxisomes are essential subcellular organelles in eukaryotic cells, which serve the degradation of various cellular metabolites (e.g. fatty acids) and the synthesis of e.g. glycerophospholipids (Wanders RJ 2014).

Peroxisomes appear as 0.2 to 1.0 µm large, round organelles surrounded by a single-layer lipid membrane. They are detected in increased density in hepatocytes.

Numerous (up to 50) mono- and dioxygenases that fuse free radicals can be detected in the peroxisomes. This restricts their reactivity. The best-known and eponymous enzymes of the peroxisomes are the peroxidases, including catalase, which inactivates hydrogen peroxide by converting it into oxygen and water (De Munter S et al. 2015).

In addition to binding free radicals, peroxisomes are able to oxidize fatty acids to acetyl-CoA. The resulting activated acetic acid can be transported into the cytosol via a transporter. Here it is available for the formation of fatty acids and cholesterol.

Mutations in the genes coding for peroxisomes, such as the PEX1 and PEX5 genes, lead to defective peroxisome function (Braverman NE et al. 2012). This results in multisystem diseases such as Zellweger syndrome and congenital adrenoleukodystrophy. Here, incorrectly saturated (more rarely unsaturated) very-long-chain fatty acids (VLCFA) such as phytanic acid, cerotic acid, brassylic acid) are deposited in the cells of particularly metabolically active organs or excreted in the urine as pathological excretion products (they are detectable in the urine) Wanders RJ (2014).

1. Braverman NE et al (2012) Functions of plasmalogen lipids in health and disease.Biochim Biophys Acta 1822:1442-2452.
2. De Munter S et al (2015) Peroxisomal Disorders: A Review onCerebellar Pathologies. Brain Pathol 25:663-678.
3. Wanders RJ (2014) Metabolic functions of peroxisomes in health and disease. Biochemistry 98:36-44.